The present invention relates to a semiconductor strain sensor, a method of processing the sensor, and a scanning probe microscope, particularly forming a Schottky-barrier by contacting metal to a beam portion of a probe made of a semiconductor substrate, detecting deflection of the probe as change of characteristic of the Schottky-barrier.
In the conventional scanning probe microscope (SPM), an exploring needle is attached at a free end of a probe, and deflection of the probe generated by movement up and down of the exploring needle response to raggedness of surface of a sample has been detected using optical interferometry of an optical polarization technique. However, there has been a problem that conventional microscope needs complex adjustment when using such an optical detecting method. On the other hand, recently a small-size, light-weight semiconductor strain sensor is widely used, which can output a deflection as an electric signal directly. The sensor is adopted for the probe of the SPM.
As shown in FIG. 20, for example, a probe-type semiconductor strain sensor comprises a cantilever arm portion (beam portion) 1 having a free end la formed by selectively etching a part of a semiconductor substrate 2 so as to have a U-shape and a gage portion 3 formed near a fixed end (root) of the cantilever arm portion 1, and the gage portion 3 detects stress/strain at a portion of the cantilever in response to deflection of the free end 1a, and the strain is converted to an electric signal and outputted.
In the conventional semiconductor strain sensor, as described in Japanese Opened Patent No. 5-196458 for example, the gage portion is constructed with piezo resistance. As the electric resistance of the piezo resistance varies by applying stress, deflection is detected by measuring a resistance change of the piezo resistance at the resistance bridge circuit, such as Wheatstone bridge or the like.
As above-mentioned, when deflection of the probe is detected as stress/strain applied to piezo resistance, as the resistance rate of change for strain of the piezo resistance, namely voltage or current rate of change, is little and sensitivity is low, not only is a complex bridge circuit needed for the detecting, but an extremely accurate adjustment of each resistance constructing the resistance bridge is also needed.
An object of the present invention is to provide a semiconductor strain sensor solving the conventional above-mentioned problem by outputting deflection of the probe with high response speed as a large signal change, a method of processing the sensor, and a scanning probe microscope adopting the semiconductor strain sensor for the probe.